HR: 14:25h
AN: V43D-03    [Abstracts]
TI: Constraints on Lava Flow Emplacement Derived From Precision Topographic Measurements
AU: * Zimbelman, J R
EM: zimbelmanj@si.edu
AF: Smithsonian Institution, CEPS/NASM MRC 315, Washington, DC 20013-7012 United States
AU: Bjonnes, E E
EM: emblue@eden.rutgers.edu
AF: Rutgers University, Dept. of Geological Sciences 610 Taylor Road, Piscataway, NJ 08854 United States
AB: Precision topography obtained with a Differential Global Positioning System (DGPS) was used to derive constraints on the physical properties of two lava flows on the Big Island of Hawaii. We used a Trimble 4800 DGPS to collect positional information across the lava flows with < 2 cm horizontal and < 4 cm vertical precision (but field tests show that points are usually repeatable to < 1 cm both horizontally and vertically). The DGPS data were overlaid on georeferenced aerial and satellite imaging data, allowing us to correlate the measured topographic points to field notes and photographs, as well as to the local setting evident in the vertical images. We combined field and imaging data for the eastern lobe of the 1907 basalt flow from the southwestern rift zone of Mauna Loa volcano, east of the Ocean View Estates subdivision, and for portions of a grass-covered Pleistocene benmoreite flow near Mana on the western flank of Mauna Kea volcano. Measured physical dimensions of the Hawaiian lava flows obtained from the DGPS data were then used to calculate the yield strength, average effusion rate, and effective viscosity of the lavas using published relationships derived from diverse theories of fluid flow. Yield strengths obtained from three different expressions ranged from 5800 to 56000 Pa for the Mauna Loa basalt flow and from 13000 to 28000 Pa for the Mauna Kea benmoreite flow. Total flow length could not be determined for the Mauna Kea flow, but the entire surface portion of the 1907 flow is well exposed; this allowed us to calculate an average effusion rate of 29 m/s and effective viscosities ranging from 17000 to 280000 Pa-s for this flow, broadly consistent with values published for the 1984 basalt flow from the eastern rift zone of Mauna Loa. These results improve our confidence in being able to derive similar constraints on the likely emplacement conditions of lava flows on other planets, such as the enormous lava flows commonly found on the martian, venusian and lunar surfaces.
DE: 5460 Physical properties of materials
DE: 5480 Volcanism (6063, 8148, 8450)
DE: 8425 Effusive volcanism
DE: 8429 Lava rheology and morphology
DE: 8450 Planetary volcanism (5480, 6063, 8148)
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005